Permitting

Are you required to pull a permit when paralleling an existing system. I have three bathrooms that need the water piping replaced but no relocation of fixtures and no additional fixtures to be added. Also we will not be replacing the service line. I am looking for the code # in UPC that I can show to the building official that a permit is not required for paralleling an existing system

Unless it has been adopted without modification by your local jurisdiction, whatever you may find in the UPC per se is irrelevant. The unamended copy of the UPC I have
at hand is quite clear that the sort of work you describe does require a permit.

Maybe there is something I don't understand. Well, there's a lot I don't understand, but in this case, I don't understand why people seem so reluctant to get a permit to do work. Some even assure us that their job won't be inspected. I find it hard to believe that someone would deliberately do illegal work, so other than a few dollars to verify the work was done properly, what's the big deal. If in doubt, get a permit. If the authorities say it isn't needed, fine, you've saves a few dollars. So what's the big deal about pulling a permit?

A permit is partially to ensure it is done correctly, but MOSTLY to update your building's records so they can increase your taxes to reflect the new status of the building. As far a water repiping is concerned it usually depends on how MUCH is being changed. I believe, but it has been a long time since I checked, that if you change more than 20% of the piping it needs a permit. It is immaterial whether you are "duplicating" an existing system or not.